Synthetic surfaces for culturing stem cell derived cardiomyocytes

ABSTRACT

Synthetic surfaces suitable for culturing stem cell derived cardiomyocytes contain acrylate polymers formed from one or more acrylate monomers. The acrylate surfaces, in many cases, are suitable for culturing stem cell derived cardiomyocytes in chemically defined media.

PRIORITY

This application claims priority to U.S. provisional Appl. No.61/062,921, filed Jan. 30, 2008, and is incorporated by reference in itsentirety.

FIELD

The present disclosure relates to cell culture articles and methods ofuse thereof, and more particularly to articles suitable for supportingthe culture of stem cell derived cardiomyocytes.

BACKGROUND

Pluripotent stem cells such as human embryonic stem cells (hESCs) havethe ability to differentiate into any of the three germ layers, givingrise to any adult cell type in the human body. This unique propertyprovides a potential for developing new treatments for a number ofserious cell degenerative diseases, such as diabetes, spinal cordinjury, heart diseases and the like. For example, unlike organs such asthe skin or liver, the heart is not capable of regenerate sufficientcardiomyocytes to undergo extensive repair. Therefore cardiac repair maybenefit from cardiomyocytes, which can be differentiated from hESCs orother pluripotent stem cells, being transplanted into the heart.

However there remain obstacles in the development of such hESC-basedtreatments. Such obstacles include obtaining and maintaining adequatenumbers of undifferentiated hESCs in tissue culture and controllingtheir differentiation in order to produce specific cell types. Stem cellcultures, such as hES cell cultures are typically seeded with a smallnumber of cells from a cell bank or stock and then amplified in theundifferentiated state until differentiation is desired for a giventherapeutic application. To accomplish this, the hESC or theirdifferentiated cells are currently cultured in the presence of surfacesor media containing animal-derived components, such as feeder layers,fetal bovine serum, or MATRIGEL. These animal-derived additions to theculture environment expose the cells to potentially harmful viruses orother infectious agents which could be transferred to patients orcompromise general culture and maintenance of the hESCs. In addition,such biological products are vulnerable to batch variation, immuneresponse and limited shelf-life.

Some steps have been taken to culture hESCs either in media or onsurfaces that are free of animal-derived components. However, theresponse of hESCs or their differentiated derivatives is difficult topredict as components of the surface or culture medium change. Yet someadvances have been made. For example, hESC-derived cardiomyocytes havebeen cultured in defined serum-free medium. While such culture systemsare not completely xeno-free culture systems when the matrices employedcontain animal-derived components, such as gelatin and MATRIGEL, they doprovide a step toward the eventual clinical application of hESC-derivedcardiomyocytes. By way of further example, some synthetic surfaces havebeen identified that can support differentiation of human epithelialstem cells into epithelial cells. However, the systems employed reliedon serum medium for the cell culture, which still potentially causesproblem as described before for all biological animal derivedcomponents. To date, a completely animal free system employing achemically defined medium and a synthetic surface has not yet beenidentified for culturing stem cells or cells derived from stem cells.

BRIEF SUMMARY

The present disclosure describes, inter alia, synthetic surfaces usefulin the culture of stem cell-derived cardiomyocytes in chemically definedmedia.

In an embodiment, a method for culturing a stem cell-derivedcardiomyocytes is provided. The method includes depositing a suspensioncontaining the stem cell-derived cardiomyocyte on a polymer material andculturing the deposited stem cell-derived cardiomyocyte in a cellculture medium. The polymer material comprises a homopolymer orcopolymer of selected one or more acrylate monomers.

In an embodiment, a culture of a stem cell-derived cardiomyocyte isprovided. The culture includes an article having a polymeric materialdisposed on a surface. The culture further includes the stemcell-derived cardiomyocyte disposed on the polymer material and aculture medium in which the stem cell-derived cardiomyocyte is cultured.The polymer material comprises a homopolymer or copolymer of selectedone or more acrylate monomers.

In an embodiment, a cell culture article for culturing stem cell-derivedcardiomyocytes in a chemically defined medium is provided. The articleincludes a substrate having a surface and a polymer material disposed onthe surface. The polymer material comprises a homopolymer or copolymerof selected one or more acrylate monomers.

One or more of the various embodiments presented herein provide one ormore advantages over prior surfaces for culturing stem cell-derivedcardiomyocytes. For example, the synthetic surfaces reduce potentialcontamination issues associated with surfaces having components obtainedfrom or derived from animal sources. Such surfaces may also provide forimproved shelf life compared to those surfaces with biologicalcomponents. The ability to culture stem cell-derived cardiomyocytes inchemically-defined media further reduces potential contamination issues.In addition, there will likely be less batch to batch variation in theability of the synthetic surfaces or chemically defined media, resultingin improved reproducibility of culture results and expectations. Theseand other advantages will be readily understood from the followingdetailed descriptions when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-B are schematic diagrams of side views of synthetic polymerlayer coated articles.

FIG. 2A-C are schematic diagrams of cross sections of a multi-well cellculture plate. The plate is uncoated in FIG. 2A and coated in FIGS.2B-C.

FIG. 3 is a fluorescent image of stem cell derived cardiomyocytescultured in chemically defined medium and on a surface of formulation 1(A), formulation 18 (B), and MATRIGEL (C) as described in Example 1.Green: Nkx 2.5. Red: Alpha-actinin.

The drawings are not necessarily to scale. Like numbers used in thefigures refer to like components, steps and the like. However, it willbe understood that the use of a number to refer to a component in agiven figure is not intended to limit the component in another figurelabeled with the same number. In addition, the use of different numbersto refer to components is not intended to indicate that the differentnumbered components cannot be the same or similar.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration several specific embodiments of devices, systems andmethods. It is to be understood that other embodiments are contemplatedand may be made without departing from the scope or spirit of thepresent disclosure. The following detailed description, therefore, isnot to be taken in a limiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

Unless stated otherwise, ratios of compounds in a composition, such as asolution, are stated on a by volume basis.

As used herein, “have”, “having”, “include”, “including”, “comprise”,“comprising” or the like are used in their open ended sense, andgenerally mean “including, but not limited to”.

As used herein the term “acrylate” includes compounds containing anacrylate moiety or a methacrylate moiety. An acrylate moiety is moietyof the following formula: CH₂CHC(O)O—. A methacrylate moiety is a moietyof the following formula: CH₂C(CH₃)C(O)O—. For the purposes of thisdisclosure, the term “acrylate” includes specific compounds disclosed inTable 1. “Acrylate” and “methacrylate” are used herein interchangeable,except when content clearly dictates otherwise; e.g. when a specificcompound or group of compounds are named.

The present disclosure describes, inter alia, articles having syntheticsurfaces for culturing stem cell-derived cardiomyocytes and methods forculturing stem cell-derived cardiomyocytes on such surfaces. In someembodiments, the synthetic surfaces are used in combination with achemically defined medium to culture stem cell-derived cardiomyocytes.The surfaces may be useful in differentiating stem cells, such as hESCs,into cardiomyocytes.

1. Cell Culture Article

Referring to FIG. 1, a schematic diagram of article 100 for culturingcells is shown. The article 100 includes a base material substrate 10having a surface 15. A synthetic polymer coating layer 20 is disposed onthe surface 15 of the base material 10. While not shown, it will beunderstood that synthetic polymer coating 20 may be disposed on aportion of base material 10. The base material 10 may be any materialsuitable for culturing cells, including a ceramic substance, a glass, aplastic, a polymer or co-polymer, any combinations thereof, or a coatingof one material on another. Such base materials 10 include glassmaterials such as soda-lime glass, pyrex glass, vycor glass, quartzglass; silicon; plastics or polymers, including dendritic polymers, suchas poly(vinyl chloride), poly(vinyl alcohol), poly(methyl methacrylate),poly(vinyl acetate-maleic anhydride), poly(dimethylsiloxane)monomethacrylate, cyclic olefin polymers, fluorocarbon polymers,polystyrenes, polypropylene, polyethyleneimine; copolymers such aspoly(vinyl acetate-co-maleic anhydride), poly(styrene-co-maleicanhydride), poly(ethylene-co-acrylic acid) or derivatives of these orthe like.

Examples of articles 100 suitable for cell culture include single andmulti-well plates, such as 6, 12, 96, 384, and 1536 well plates, jars,petri dishes, flasks, beakers, plates, roller bottles, slides, such aschambered and multichambered culture slides, tubes, cover slips, cups,spinner bottles, perfusion chambers, bioreactors, and fermenters.

Synthetic polymer coating 20 provides a surface 25 on which cells may becultured. The synthetic polymer surface 20 includes polymerized(meth)acrylate monomers, selected from the group of monomers provided inTable 1 below. Other materials (not shown), such as peptides, may beincorporated into or conjugated to synthetic polymer surface to producea biomimetic surface.

TABLE 1 List of acrylate and methacrylate monomers Monomer name Monomerstructure Tetra(ethylene glycol) diacrylate

Glycerol dimethacrylate

Triethylene glycol dimethacrylate

1,4-Butanediol dimethacrylate

Poly(ethylene glycol) diacrylate (average M_(n) ~258)

Di(ethylene glycol) dimethacrylate

Tetra(ethylene glycol) dimethacrylate

1,6-Hexanediol propoxylate diacrylate

Neopentyl glycol diacrylate

Neopentyl glycol dimethacrylate

Trimethylolpropane benzoate diacrylate

Trimethylolpropane ethoxylate (1 EO/OH) methyl

Tricyclo[5.2.1.0^(2,6)]decane- dimethanol diacrylate

Neopentyl glycol ethoxylate diacrylate

Trimethylolpropane triacrylate

The acrylates listed in Table 1 may be synthesized as known in the artor obtained from a commercial vendor, such as Polysciences, Inc., SigmaAldrich, Inc., and Sartomer, Inc.

As shown in FIG. 1B, an intermediate layer 30 may be disposed betweensurface 15 of base material 10 and the synthetic polymer coating 20.Intermediate layer 30 may be configured to improve binding of coating 20to substrate 10, to facilitate monomer spreading, to render portions ofthe surface 10 that are uncoated cytophobic to encourage cell growth oncoated areas, to provide a substrate compatible with a monomer orsolvent where the monomer or solvent is incompatible with the basematerial 10, to provide topographical features if desired through, forexample, patterned printing, or the like. For example, if substrate 10is a glass substrate, it may be desirable to treat a surface of theglass substrate with an epoxy coating or a silane coating. For variouspolymer base materials 10 it may be desirable to provide an intermediatelayer 30 of polyamide, polyimide, polypropylene, polyethtylene, orpolyacrylate. While not shown, it will be understood that syntheticpolymer coating 20 may be disposed on a portion of intermediate layer30. It will be further understood that intermediate layer 30 may bedisposed on a portion of base material 10.

In various embodiments, surface 15 of base material 10 is treated,either physically or chemically, to impart a desirable property orcharacteristic to the surface 15. For example, and as discussed below,surface 15 may be corona treated or plasma treated. Examples of vacuumor atmospheric pressure plasma include radio frequency (RF) andmicrowave plasmas both primary and secondary, dielectric barrierdischarge, and corona discharge generated in molecular or mixed gasesincluding air, oxygen, nitrogen, argon, carbon dioxide, nitrous oxide,or water vapor.

Synthetic polymer coating layer 20, whether disposed on an intermediatelayer 30 or base material 10, preferably uniformly coats the underlyingsubstrate. By “uniformly coated”, it is meant that the layer 20 in agiven area, for example a surface of a well of a culture plate,completely coats the area at a thickness of about 5 nm or greater. Whilethe thickness of a uniformly coated surface may vary across the surface,there are no areas of the uniformly coated surfaces through which theunderlying layer (either intermediate layer 30 or base material 10) isexposed. Cell responses across non-uniform surfaces tend to be morevariable than cell responses across uniform surfaces.

Synthetic polymer coating layer 20 may have any desirable thickness.However, it has been found that thicker coatings, e.g. coatings ofgreater than about 10 micrometers, tend to have unevenness around theperiphery of the coating due to surface tension. In various embodiments,the thickness of the coating layer 20 is less than about 10 micrometers.For example, the thickness may be less than about 5 micrometers, lessthan about 2 micrometers, less than about 1 micrometers, less than about0.5 micrometers or less than about 0.1 micrometers.

The polymer material forming synthetic polymer layer 20 may becross-linked to any suitable degree. Higher degrees of cross-linking mayresult in reduced waste product and reduced cell toxicity.

Article 100, in numerous embodiments, is cell culture ware having awell, such as a petri dish, a multi-well plate, a flask, a beaker orother container having a well. Referring now to FIG. 2, article 100formed from base material 10 may include one or more wells 50. Well 50includes a sidewall 55 and a surface 15. Referring to FIG. 2B-C, asynthetic polymer coating 20 may be disposed on surface 15 or sidewalls55 (or, as discussed above with regard to FIG. 1 one or moreintermediate layer 30 may be disposed between surface 15 or sidewall 55and synthetic polymer coating 20) or a portion thereof.

In various embodiments, article 100 includes a uniformly coated layer 20having a surface 25 with an area greater than about 5 mm². When the areaof the surface 15 is too small, reliable cell responses may not bereadily observable because some cells, such as human embryonic stemcells, are seeded as colonies or clusters of cells (e.g., having adiameter of about 0.5 mm) and adequate surface is desirable to ensureattachment of sufficient numbers of colonies to produce a quantitativecell response. In numerous embodiments, an article 100 has a well 50having a uniformly coated surface 15, where the surface 15 has an areagreater than about 0.1 cm², greater than about 0.3 cm², greater thanabout 0.9 cm², or greater than about 1 cm².

2. Coating of Synthetic Polymer Layer

A synthetic polymer layer may be disposed on a surface of a cell culturearticle via any known or future developed process. Preferably, thesynthetic polymer layer provides a uniform layer that does notdelaminate during typical cell culture conditions. The synthetic polymersurface may be associated with the base material substrate via covalentor non-covalent interactions. Examples of non-covalent interactions thatmay associate the synthetic polymer surface with the substrate includechemical adsorption, hydrogen bonding, surface interpenetration, ionicbonding, van der Waals forces, hydrophobic interactions, dipole-dipoleinteractions, mechanical interlocking, and combinations thereof.

In various embodiments, the base material substrate surface is coatedaccording to the teachings of co-pending application Ser. No. ______,filed on even date herewith, naming Gehman et al. as inventors, havingattorney docket number 20726, and entitled STEM CELL CULTURE ARTICLE ANDSCREENING, which is hereby incorporated herein by reference in itsentirety for all purposes to the extent that it does not conflict withthe disclosure presented herein.

In numerous embodiments, monomers are deposited on a surface of a cellculture article and polymerized in situ. In such embodiments, the basematerial will be referred to herein as the “substrate” on which thesynthetic polymer material is deposited. Polymerization may be done insolution phase or in bulk phase.

As many of the monomers identified in Table 1 above are viscous, it maybe desirable to dilute the monomers in a suitable solvent to reduceviscosity prior to being dispensed on the surface. Reducing viscositymay allow for thinner and more uniform layers of the synthetic polymermaterial to be formed. One of skill in the art will be able to readilyselect a suitable solvent. Preferably the solvent is compatible with thematerial forming the cell culture article and the monomers. It may bedesirable to select a monomer that is non-toxic to the cells to becultured and that does not interfere with the polymerization reaction.Alternatively, or in addition, selection of a solvent that can besubstantially completely removed or removed to an extent that it isnon-toxic or no longer interferes with polymerization may be desirable.In such circumstances, it may be desirable that the solvent be readilyremovable without harsh conditions, such as vacuum or extreme heat.Volatile solvents are examples of such readily removable solvents.

Some solvents that may be suitable in various situations for coatingarticles as described herein include ethanol, isopropanol, acetylacetate, dimethylformamide (DMF), and dimethylsulfoxide (DMSO). Asdescribed in co-pending application Ser. No. ______, ethanol may be aparticularly suitable solvent when it is desired to remove solvent priorto polymerization.

The monomers may be diluted with solvent by any suitable amount toachieve the desired viscosity and monomer concentration. Generally themonomer compositions used according to the teachings presented hereincontain between about 1% to about 99% monomer. By way of example, themonomer may be diluted with an ethanol solvent to provide a compositionhaving between about 1% and about 50% monomer, or from about 1% to about10% monomer by volume. The monomers may be diluted with solvent so thatthe polymer layer 20 achieves a desired thickness. As discussed above,if the deposited monomers are too thick, a non-uniform surface mayresult. As described in further details in the Examples, non-uniformsurfaces may be observed when the monomer-solvent composition isdeposited on a surface 15 of a well 50 at a volume of greater than about8 microliters per square centimeter of the surface 15. In variousembodiments, the monomer-solvent compositions are deposited on a surface15 of a well 50 in a volume of about 7 microliters or less per squarecentimeter of the surface 15. For example, the monomer-solventcompositions may be deposited on a surface 15 of a well 50 in a volumeof about 5 microliters or less per square centimeter of the surface 15,or about 2 microliters or less per square centimeter of the surface 15.

In various embodiments, synthetic polymer surface is deposited on asurface of an intermediate layer that is associated with the basematerial via covalent or non-covalent interactions, either directly orvia one or more additional intermediate layers (not shown). In suchembodiments, the intermediate layer will be referred to herein as the“substrate” onto which the synthetic polymer surface is deposited.

In various embodiments, the surface of the base material is treated. Thesurface may be treated to improve binding of the synthetic polymersurface to the base material surface, to facilitate monomer spreading onthe base material surface, or the like. Of course, the base material maybe treated for similar purposes with regard to an intermediate layer. Invarious embodiments, the surface is corona treated or vacuum plasmatreated. High surface energy obtainable from such treatments mayfacilitate monomer spreading and uniform coating. Examples of vacuumplasma treatment that may be employed include microwave vacuum plasmatreatments and radio frequency vacuum plasma treatments. The vacuumplasma treatments may be performed in the presence of reactive gases,such as oxygen, nitrogen, ammonia or nitric oxide.

To form the synthetic polymer surface, one or more monomers presented inTable 1 above are polymerized. If one monomer is used, the polymer willbe referred to as a homopolymer of the monomer. If two or more differentmonomers are used, the polymer will be referred to as a copolymer of themonomers. The monomers employed may be monofunctional, difunctional, orhigher-functional. When two or more monomers are used, the ratio of themonomers may be varied. In various embodiments, two monomers are usedand the ratio, by volume of the first monomer to the second monomerranges from between about 5:95 to about 95:5. For example, the ratio ofthe first monomer to the second monomer ranges from between about 10:90to about 90:10, about 20:80 to about 80:20, from about 30:70 to about70:30. In some embodiments, the ratio of the first monomer to the secondmonomer is about 50:50, 30:70, or 10:90. It will be understood that themolecular weight of the polymer may be controlled by varying theconcentration of monomers or the ratios of difunctional orhigher-functional monomers to monofunctional monomers. Increasedconcentrations of difunctional or higher-functional monomers willincrease the degree of cross-linking in the chains.

In addition to the monomers that form the polymer layer, a compositionforming the layer may include one or more additional compounds such assurfactants, wetting agents, photoinitiators, thermal initiators,catalysts, activators, and cross-linking agents.

Any suitable polymerization initiator may be employed. One of skill inthe art will readily be able to select a suitable initiator, e.g. aradical initiator or a cationic initiator, suitable for use with themonomers listed in Table 1. In various embodiments, UV light is used togenerate free radical monomers to initiate chain polymerization.

Any suitable initiator may be used. Examples of polymerizationinitiators include organic peroxides, azo compounds, quinones, nitrosocompounds, acyl halides, hydrazones, mercapto compounds, pyryliumcompounds, imidazoles, chlorotriazines, benzoin, benzoin alkyl ethers,diketones, phenones, or mixtures thereof. Examples of suitablecommercially available, ultraviolet-activated and visiblelight-activated photoinitiators have tradenames such as IRGACURE 651,IRGACURE 184, IRGACURE 369, IRGACURE 819, DAROCUR 4265 and DAROCUR 1173commercially available from Ciba Specialty Chemicals, Tarrytown, N.Y.and LUCIRIN TPO and LUCIRIN TPO-L commercially available from BASF(Charlotte, N.C.)

A photosensitizer may also be included in a suitable initiator system.Representative photosensitizers have carbonyl groups or tertiary aminogroups or mixtures thereof. Photosensitizers having a carbonyl groupsinclude benzophenone, acetophenone, benzil, benzaldehyde,o-chlorobenzaldehyde, xanthone, thioxanthone, 9,10-anthraquinone, andother aromatic ketones. Photosensitizers having tertiary amines includemethyldiethanolamine, ethyldiethanolamine, triethanolamine,phenylmethyl-ethanolamine, and dimethylaminoethylbenzoate. Commerciallyavailable photosensitizers include QUANTICURE ITX, QUANTICURE QTX,QUANTICURE PTX, QUANTICURE EPD from Biddle Sawyer Corp.

In general, the amount of photosensitizer or photoinitiator system mayvary from about 0.01 to 10% by weight.

Examples of cationic initiators include salts of onium cations, such asarylsulfonium salts, as well as organometallic salts such as ion arenesystems.

In various embodiments where the monomers are diluted in solvent beforebeing deposited on the substrate surface, the solvent is removed priorto polymerizing. The solvent may be removed by any suitable mechanism orprocess. As described in copending application Ser. No. ______, it hasbeen found that removal of substantially all of the solvent prior tocuring, allows for better control of curing kinetics and the amount ofmonomer converted. When conversion rates of the monomers are increased,waste generation and cytotoxicity are reduced.

Whether polymerized in bulk phase (substantially solvent free) orsolvent phase, the monomers are polymerized via an appropriateinitiation mechanism. Many of such mechanisms are well known in the art.For example, temperature may be increased to activate a thermalinitiator, photoinitiators may be activated by exposure to appropriatewavelength of light, or the like. According to numerous embodiments, themonomer or monomer mixture is cured using UV light. The curingpreferably occurs under inert gas protection, such as nitrogenprotection, to prevent oxygen inhibition. Suitable UV light combinedwith gas protection may increase polymer conversion, insure coatingintegrity and reduce cytotoxicity.

The cured synthetic polymer layer may be washed with solvent one or moretimes to remove impurities such as unreacted monomers or low molecularweight polymer species. In various embodiments, the layer is washed withan ethanol solvent, e.g. greater than about 70% ethanol, greater thanabout 90% ethanol, greater than about 95% ethanol or greater than about99% ethanol. Washing with an ethanol solvent may not only serve toremove impurities, which may be cytotoxic, but also can serve tosterilize the surface prior to incubation with cells.

3. Incubating Cells on Synthetic Polymer Layer

Stem cell-derived cardiomyocytes may be cultured on a synthetic polymerlayer, as described above, according to any suitable protocol. As usedherein, “stem cell derived cardiomyocyte” means a cardiomyocyte obtainedfrom differentiation of a stem cell. In some embodiments, the stem cellsare multipotent, totipotent, or pluripotent stem cells. In someembodiments the cells may be present in an organ or tissue of a subject.In numerous embodiments, the stem cells are embryonic stem cells, suchas human embryonic stem cells.

Because human embryonic stem cells (hES) have the ability to growncontinually in culture in an undifferentiated state, the hES cells foruse in this invention may be obtained from an established cell line.Examples of human embryonic stem cell lines that have been establishedinclude, but are not limited to, H1, H7, H9, 1113 or H14 (available fromWiCell established by the University of Wisconsin) (Thompson (1998)Science 282:1145); hESBGN-01, hESBGN-02, hESBGN-03 (BresaGen, Inc.,Athens, Ga.); HES-1, HES-2, HES-3, HES-4, HES-5, HES-6 (from ES CellInternational, Inc., Singapore); HSF-1, HSF-6 (from University ofCalifornia at San Francisco); I 3, I 3.2, I 3.3, I 4, I 6, I 6.2, J 3, J3.2 (derived at the Technion-Israel Institute of Technology, Haifa,Israel); UCSF-1 and UCSF-2 (Genbacev et al., Fertil. Steril.83(5):1517-29, 2005); lines HUES 1-17 (Cowan et al., NEJM350(13):1353-56, 2004); and line ACT-14 (Klimanskaya et al., Lancet,365(9471):1636-41, 2005). Embryonic stem cells used in the invention mayalso be obtained directly from primary embryonic tissue. Typically thisis done using frozen in vitro fertilized eggs at the blastocyst stage,which would otherwise be discarded.

Cardiomyocytes according to the invention may also be differentiatedfrom induced primate pluripotent stem (iPS) cells. iPS cells refer tocells, obtained from a juvenile or adult mammal such as a human, thatare genetically modified, e.g., by transfection with one or moreappropriate vectors, such that they are reprogrammed to attain thephenotype of a pluripotent stem cell such as an hES cell. Phenotypictraits attained by these reprogrammed cells include morphologyresembling stem cells isolated from a blastocyst as well as surfaceantigen expression, gene expression and telomerase activity resemblingblastocyst derived embryonic stem cells. The iPS cells typically havethe ability to differentiate into at least one cell type from each ofthe primary germ layers: ectoderm, endoderm and mesoderm and thus aresuitable for differentiation into cardiomyocytes. The iPS cells, likehES cells, also form teratomas when injected into immuno-deficient mice,e.g., SCID mice. (Takahashi et al., (2007) Cell 131(5):861; Yu et al.,(2007) Science 318:5858).

Stem cell derived cardiomyocytes may be obtained by any suitablemethods. One way to obtain such cells is described in Laflamme et al.,“Cardiomyocytes derived from human embryonic stem cells in pro-survivalfactors enhance function of infracted rats, Nature Biotechnology, 25:1015-1024 (2007). Briefly, undifferentiated human embryonic stem cells,such as those derived from the female H7 human embryonic stem cell line,may be seeded on MATRIGEL-coated plates at a density of about 100,000cells/cm² and refer daily with hES cell growth medium (KO DMEM+20% Serumreplacement, 1 mM 1-glutamine, 1% NEAA, 0.1 mM 2-ME plus hbFGF at 80ng/ml and TGFb1 at 0.5 ng/ml) To induce differentiation, growth mediamay be replaced with RPMI-B27 medium (available from Invitrogen)supplemented with about 100 ng/ml human recombinant activin A (availablefrom R&D Systems) for about 24 hours, followed by 10 ng/ml humanrecombinant BMP4 (available from R&D Systems) for four days. Of course,any other suitable method may be employed (see, e.g., U.S. Pat. No.7,425,448).

Prior to seeding cells, the cells may be harvested and suspended in asuitable medium, such as a growth medium in which the cells are to becultured once seeded onto the surface. For example, the cells may besuspended in and cultured in serum-containing medium, a conditionedmedium, or a chemically-defined medium. As used herein,“chemically-defined medium” means cell culture media that contains nocomponents of unknown composition. Chemically defined media may, invarious embodiments, contain no proteins, hydrosylates, or peptides ofunknown origin. In some embodiments, conditioned media containspolypeptides or proteins of known composition, such as recombinantgrowth hormones. Because all components of chemically-defined media havea known chemical structure and composition, variability in cultureconditions can be reduced and thus cell response may be morereproducible. In addition, the possibility of contamination is reduced.Further, the ability to scale up is made easier due, at least in part,to the factors discussed above. Chemically defined cell culture mediaare commercially available from Invitrogen (Invitrogen Corporation, 1600Faraday Avenue, PO Box 6482, Carlsbad, Calif. 92008) as StemPro® a fullydefined, serum- and feeder-free medium (SFM) specially formulated forthe growth and expansion of human embryonic stem cells (hESCs) andStemCell Technologies, Inc as mTeSR™ 1 maintenance media for humanembryonic stem cells.

The cells may be seeded at any suitable concentration. Typically, thecells are seeded at about 10,000 cells/cm² of substrate to about 500,000cells/cm². For example, cells may be seeded at about 50,000 cells/cm² ofsubstrate to about 150,000 cells/cm². However, higher and lowerconcentrations may readily be used. The incubation time and conditions,such as temperature CO₂ and O₂ levels, growth medium, and the like, willdepend on the nature of the cells being cultured and can be readilymodified. The amount of time that the cells are incubated on the surfacemay vary depending on the cell response being studied or the cellresponse desired.

Any suitable method may be used, if desired, to confirm that the stemcell derived cardiomyocytes are indeed cardiomyocytes or that the stemcells employed have successfully differentiated into cardiomyocytes. Forexample, the presence of certain cardiomyocyte-selective markers may beinvestigated. Such markers include Nkx2.5 and a-actinin, cardiactroponin I. Antibodies to such markers may be used in standardimmunocytochemical or flow cytometry techniques. In addition oralternatively, cellular morphology or functionality, by observingbeating cardiomyocytes in culture or by performing variouselectrophysiological analyses to determine whether the cells havecharacteristics of cardiomyocytes.

The cultured stem cell derived cardiomyocytes may be used for anysuitable purpose, including investigational studies in culture, inanimals, for developing therapeutic uses, for drug discovery andtoxicology or for therapeutic purposes. One potential therapeutic orinvestigational purpose is repairing cardiac damage due to an infarct,e.g., as described in Laflamme et al., Nature Biotechnology, 25:1015-1024 (2007). The cells may also be used to create cDNA librariesaccording to known methods. The cDNA libraries may be used to study geneexpression in the differentiated cardiomyocytes. For example the libraryobtained from the differentiated cardiomyocytes may be compared to acDNA library from the undifferentiated stem cells from which thecardiomyocytes were derived, thus allowing for the identification andisolation of genes related to the differentiation and development ofcardiomyocytes.

In the following, non-limiting examples are presented, which describevarious embodiments of the articles and methods discussed above.

EXAMPLES Example 1 Identification of Acrylic Coating Surfaces Suitablefor Culturing Stem Cell Derived Cardiomyocytes in a Chemically DefinedMedium

1. Coating Preparation

Acrylic coating surfaces were prepared from homomonomers or copolymersof various acrylate and methacrylate monomers. For copolymers twodifferent acrylate or methacrylate monomers were used. Briefly, themonomers were mixed with 1% w/w of photoinitiator Irgacure 819 (CibaSpecialty Chemiscals, Inc.) and used along or blended with other monomerformulation (monomer with 1% w/w of photoinitiator) according to volumeratio of 70:30. Then formulation was placed in a well of a vacuum plasmatreated cyclic olefin copolymer plate (provided by Corning Life ScienceDevelopment group) at a volume of 2.5 μL. The plate was allowed to layhorizontally flat for 30 min for the formulation to spread out. Thecoatings were cured with 13 mW/cm² pulsed (100 Hz) UV light (XenonRC-700) for 1 min in N₂ purged box (with fused silica window). All theplates were sterilized by 25-35 kGy Gamma radiation prior to cellculture.

2. Cell Preparation and Assays

Prior to the experiments, H7 hES cells were maintained in theundifferentiated state on MATRIGEL-coated plates in SR medium (KO-DMEM,20% KO-serum replacement, 1 mM L-glutamine, 0.1 mM β-mercaptoethanol, 1%non-essential amino acids, 80 ng/ml hbFGF and 0.5 ng/ml TGFb1).hESC-derived cardiomyocytes were generated using direct differentiationprotocol. Briefly, undifferentiated H7 cells were harvested by 200 U/mlcollagenase IV and seeded on MATRIGEL-coated plates at the density of100,000 cells/cm² in SR medium. Cells were cultured for 6 days withdaily medium exchange. Cardiac differentiation was initiated byreplacing SR medium with RPMI-B27 medium, supplemented with 100 ng/mlhuman recombinant activin A for 24 h, followed by 10 ng/ml humanrecombinant BMP4 for 4 days. At this point, cells were detached byAccutase treatment, re-suspended in RPMI-B27 medium w/o growth factors,and seeded at the density of 100,000 cells/cm² onto Corning CB/TOPAS96-well plates coated with different binary mixtures of acrylates orMATRIGEL as positive control. Cells were cultured for another 2-3 weekswith the same medium exchange every 2-3 days. The wells weremicroscopically examined, and spontaneous beating activity was recorded.

At the end of the differentiation protocol, cells were fixed with 4%paraformaldehyde immunostained for cardiomyocyte (CM) specific markers,Nkx2.5 and a-actinin, and counterstained with4′-6-Diamidino-2-phenylindole (DAPI) to stain the nucleus. Afterscanning each plate with ArrayScan, the following quantitative analyseswere performed for each surface: 1) TNC: total number of cells based onDAPI positive cell number, 2) TNC: total number of CM, based onNkx2.5-positive cell number, 3) CM yield=TNC/TNC.

3. Results

It was found that only a small portion of the tested surfaces supportedthe cell growth while maintaining some key characteristics andfunctions. Examples of the coating surfaces which supported growth ofdifferentiated human embryonic cardiomyocytes in chemically definedmedium are listed in Table 2, where the volume ratio of monomer (1) tomonomer (2) is 70:30. These surfaces were characterized and given a“grade” based on qualitative assessments of the morphology of the cellsand their adhesion to the surfaces. Acrylate surface rating wasperformed based on consideration of the following criteria: 1) totalcell number, 2) total CM number, 3) CM yield, 4) presence of beatingareas, 5) similarity to Matrigel derived CM morphology. Notes on thequalities of the differentiated embryonic myocytes that were observedare shown in Table 2, as well as the grade that was assessed. Forexample, “Sim MA” is a note that indicates that cells growing on thatsurface were similar to cells growing on Matrigel™ “Sim TOP” is a notethat indicates that the cells growing on that surface were similar tocells growing on plasma-treated cyclic olefin copolymer surface, sold asTOPAS® surface by TOPAS, Florence, Kentucky. The notes also indicatethat some of the surfaces supported differentiated embryonic myocytesthat began to beat in culture.

TABLE 2 Example compositions of acrylic polymers which support theculture of hES cell derived cardiomyocytes in chemically defined medium.Formua- tion ID Monomer (1) Monomer (2)  95-1 Tetra(ethylene glycol)diacrylate 100%  95-2 Glycerol dimethacrylate 100%  90-2 Triethyleneglycol dimethacrylate 100%  90-4 1,4-Butanediol dimethacrylate 100% 95-3 Poly(ethylene glycol) diacrylate 100% 122-1 Tetra(ethylene glycol)Glycerol dimethacrylate 30% diacrylate 70% 122-3 Tetra(ethylene glycol)1,4-Butanediol dimethacrylate diacrylate 70% 30%  27-2 Tetra(ethyleneglycol) Trimethylolpropane diacrylate 70% triacrylate 30% 123-1 Glyceroldimethacrylate 70% Tetra(ethylene glycol) diacrylate 30% 123-2 Glyceroldimethacrylate 70% Tri(ethylene glycol) dimethacrylate 30% 123-3Glycerol dimethacrylate70% 1,4-Butanediol dimethacrylate 30% 123-4Glycerol dimethacrylate 70% Poly(ethylene glycol) diacrylate 30% 123-6Triethylene glycol Glycerol dimethacrylate 30% dimethacrylate 70% 123-7Triethylene glycol 1,4-Butanediol dimethacrylate 70% dimethacrylate 30%124-2 1,4-Butanediol dimethacrylate Glycerol dimethacrylate 30% 70%124-3 1,4-Butanediol dimethacrylate Triethylene glycol 70%dimethacrylate 30% 124-5 Poly(ethylene glycol) Tetra(ethylene glycol)diacrylate 70% diacrylate 30% 133-1 Di(ethylene glycol) Tetraethyleneglycol dimethacrylate 70% dimethacrylate 30% 134-1 Tetraethylene glycolDi(ethylene glycol) dimethacrylate 70% dimethacrylate 30% 140-1Trimethylolpropane Neopentyl glycol ethoxylate triacrylate 70%diacrylate 30%

TABLE 3 Cell count, cell surface Marker, and functions of h7differentiated cardiomyocyted cultured on acrylate polymer surfaces.Average Cell Count Average Cardio yield Rat- Beat- (per % (based on IDing ing well) Nkx2.5 count*Nkx2.5) Note  95-2 A y 19970 7 1397.9 Sim MA 90-2  C− 5420 14 758.8 Sim MA, peeled lumpy  90-4  B− y 6907 24 1657.68Sim TOP  95-3 C y 3788 24 909.12 122-3 B 6061 3 181.83 Sim as MA, notbeating 123-1  B+ y 5250 5 262.5 Sim MA, beating 123-2 A 6327 7 442.89Good attachment, no beating 123-3 A 6223 8 497.84 Good attachment, nobeating 123-4  B− 4954 4 198.16 Many attached, dying 123-7 C 4246 15636.9 peeled 124-2 A y 3798 21 797.58 Sim TOP beating 124-3 B y 2267 8497.84 Sim TOP beating 124-5 C y 940 27 253.8 Beating but poorattachment 140-1  B− y 2886 33 952.38 Sim TOP

For other tested homopolymers and copolymer combinations, very low or nocardiomyocytes yield was observed at the end of the differentiationprocedure, due to either low total cell number or low Nkx2.5-positivecells present on those surfaces

FIG. 3 shows fluorescent images of differentiated cardiomyocytescultured on surfaces of formulation 95-2 (A), formulation 27-2 (B), andMATRIGEL (C). Cell morphology, Nkx 2.5 marker expression (green) andalpha-actinin marker expression (red) are similar to MATRIGEL. Inaddition, the cells depicted in FIG. 3 exhibited beating prior to fixingwith paraformaldehyde.

Thus, embodiments of SYNTHETIC SURFACES FOR CULTURING STEM CELL DERIVEDCARDIOMYOCYTES are disclosed. One skilled in the art will appreciatethat the arrays, compositions, kits and methods described herein can bepracticed with embodiments other than those disclosed. The disclosedembodiments are presented for purposes of illustration and notlimitation.

1-22. (canceled)
 23. A cell culture comprising a beating cell expressingNkx2.5 disposed on a surface comprising a diacrylate or adimethacrylate.
 24. The cell culture of claim 23 wherein the beatingcell expressing Nkx2.5 is derived from a culture of pluripotent stemcells.
 25. The cell culture of claim 23, wherein the beating cellexpressing Nkx2.5 is a human cell.
 26. The cell culture of claim 1,wherein the dimethacrylate is glycerol dimethacrylate.
 27. The cellculture of claim 23, wherein the diacrylate is poly(ethylene glycol)diacrylate.
 28. The cell culture of claim 23, wherein the dimethacrylateis 1,4-butanediol dimethacrylate.
 29. A cell culture comprising a cellexpressing Nkx2.5 disposed on a surface comprising a diacrylate or adimethacrylate.
 30. The cell culture of claim 29 wherein the cellexpressing Nkx2.5 is derived from a culture of pluripotent stem cells.31. The cell culture of claim 29, wherein the cell expressing Nkx2.5 isa human cell.
 32. The cell culture of claim 29, wherein thedimethacrylate is glycerol dimethacrylate.
 33. The cell culture of claim29, wherein the diacrylate is poly(ethylene glycol) diacrylate.
 34. Thecell culture of claim 29, wherein the dimethacrylate is 1,4-butanedioldimethacrylate.